1. Field of the Invention
The present invention relates generally to detection of presence of assets in an area, and more specifically, to an asset presence detection and location finding system for implementation in wireless local area network environments.
2. Background of the Invention
Wireless asset detection and tracking systems are increasing in prevalence as wireless systems are incorporated in buildings and other areas such as Internet kiosks and lounges. Additionally, radio-frequency identification (RFID) tags have been in use for many years for tracking assets, such as in shipping yards and facilities and in consumer outlets for inventory and theft management.
The above-incorporated parent application discloses an RFID tag system using a Wireless Local Area Network (WLAN) channel that takes advantage of existing WLAN infrastructure to locate RFID tags. However, in some applications it is not necessary or cost-effective to provide enough access points (APs) or location units, determine times-of-arrival and perform triangulation to fully locate a tag or other transmitting device in a WLAN environment, when all that is necessary is that the presence of an asset be detected.
Presence detectors have also been in use for many years in many applications, but not generally in wireless networks for the purpose of detecting the presence of assets. Generally, the detection of the presence of a WLAN unit results in the connection of the WLAN unit to the AP after which presence can be confirmed or no connection may result, after which the presence of a “rogue” device may be confirmed. However, in either case, the goal is generally to connect the WLAN unit to the wireless network via the AP. Further, WLAN APs and other units typically provide no means for detecting any device (WLAN-compatible or not) that is not attempting connection on a particular AP's channel, or at least attempting to locate a device for connection to an AP via a probe request message (in 802.11 revision systems).
It would also be useful to incorporate location-finding in a WLAN either in combination with presence detection or separately, without requiring that the device being located associate with the network or attempt association with the network.
Therefore, it would be desirable to provide a presence detection system for detecting WLAN compatible transmitters using units of a wireless network, without requiring a separate asset tracking system, and without disrupting operation of the WLAN.